Method of electrolytically recovering metals.



. W. A. HUSSEY.

METHOD OF ELECTROLYTICALLY RECOVERING METALS.

APPLICATION FILED APR. 15. I913.

1 ,207 ,048. Patented Dec. 5, 1916.

2 SHEETSSHEET l- WITNESSES INVENTOR v @1104; d. M 4

BY I," MMW,

ATTORNEY W. A. HUSSEY.

METHOD OF ELECTROLYTICALLY RECOVERING METALS.

APPLICATION FILED APR. 15. 1913.

1,207,048. Patented Dec. 5,1916.

2 $HEETS$HEET 2.

WITNESSES INVENTOR J M11114; 0 Macy $411.): b1. /vu -C c ATTORNEY TE STATES PATENT oEEoE.

WILLIAM A. HUSSEY, OF OAKLAND, CALIFORNIA, ASSIGNOR, BY MESNE ASSIGNMENTS, OF ONE-HALF TO JAMES H. ALLING AND ONE-HALF TO FRANCIS M. WRIGHT, BOTH OF SAN FRANCISCO, CALIFORNIA.

METHOD OF ELECTROLYTICALLY RECOVERING METALS.

Specification of Letters Patent.

Patented Dec. 5, 1916.

Original application filed June 26, 1912, Serial No. 705,947. Divided and this application filed April 15,

To all whom it may concern? Be it known that I, WILLIAM A. HUssEY, a citizen of the United States, residing at Oakland, in the county of Alameda and State of California, have invented new and useful Improvements in Methods of Electrolytically Recovering Metals, of which the following is a specification.

The present invention relates to an improved method of recovering precious metals from pulverized ores containing the same, and is a division of an application filed June 26, 1912, Serial Number 705,947, the object of the invention being to provide vsuch a method by which said recovery may be more complete than heretofore, effected in much less time, and at a low cost, and with which the operation can be carried on continuously without interruptions except only for the removal of the recovered metals and then at only long intervals of time.

In the accompanying drawing, Figure 1 is a broken vertical longitudinal section of an apparatus for carrying out my improved process; Fig. 2 is a similar view of another form thereof; and Fig. 3 is a diagrammatic View of two electrolytic machines by which my improved process is carried out.

Referring to the drawing, 1 indicates the main body of an apparatus for practising my improved process, composed of insulating material, such as vulcanized rubber, the upper surface of which is formed with a longitudinal series of recesses or depressions 2 forming electrolytic cells, and which is arranged at any suitable inclination. Said apparatus is more fully described in the parent application hereinbefore referred to.

The height of the upper end of the apparatus is considerably greater than that of the lower end, so that each cell is at a corresponding depth below the preceding cell and at a corresponding height above the next succeeding cell.

In the bottom of each cell 2, at the upper end thereof, is secured, by a suitable conducting bolt 9, a transverse cathode bar 11 of any suitable metallic material. 12 indicates a cover which fits closely upon the upper raised edges of the sides 13 of the body of the apparatus and entirely excludes the light from the interior thereof and Serial No. 761,247.

prevents the escape of gases directly upward, their longitudinal escape being prevented when the apparatus is in operation by the water flowing into and out of the apparatus, and secured to said cover 12 between said sides 13 are holders 14 of any suitable insulating material arranged in longitudinal series, one above each of the said cells 2.

In the form of the apparatus shown in Fig. 1, there is secured in a recess in the lower end of each holder, an anode 15, )referably of graphite or other suitable material, and in a recess in the upper portion of each holder a pole 16, also of graphite or other suitable material. Each cell is, as shown at 17, filled with mercury to a suitable depth. All the anodes 15 are electrically connected by wires 18, and a wire 10, to the positive pole of an electric generator, and all the cathode plates or bars 11 are also electrically connected by means of their bolts 9, and a wire 19, to the negative pole of said machine. A wire 20 electrically connects each pole 16 outside the apparatus with the corresponding bar 11.

I shall first explain the nature of the process employed in the form of apparatus shown in Fig. 1, before describing the second form thereof. In this process the pulp to be treated, mixed with a certain'proportion of sodium cyanid solution, is fed into the apparatus, the electric generator being supposed in operation. On arriving at the first cell and being subjected to electrolysis, sodium cyanid is decomposed, nascent cyanogen being liberated at the anode, and sodium being deposited on the mercury cathode, and probably forming therewith sodium amalgam. It is found that the mercury and sodium at the surface are, by the force of the electric current, on account of the anode being located at the discharge end of the cell and the cathode in the intake end thereof, driven in a direction against the flow of the pulp into the intake part of the cell, out of the region of electrolysis. The sodium decompses the water to form caustic soda, and nascent hydrogen is given off. the nascent cyanogen in the presence of alkali dissolves the fine particles of gold, and the caustic soda immediately decomposes any v organic or greasy particles upon the gold place, forms in effect a voltaic cell, generat-.

ing electricity, which, unless the circuit be completed through said cell, would render the pole 16 polarized, and thus generate a counter electro-motive force, and which would thus prevent any further abovedescribed action of said voltaic cell. It is for this reason that I connect each electrode 16 with the corresponding bar 9 by a conductor 20 outside of the cell, so that thecurrent generated may be conducted away and the counter electro-motive force be no longer developed. It is found that said current thus generated has a difference of potential of about two volts. posed of an electrolytic region, in which electrolysis takes place, and a voltaic region, in which chemical reactions occur tending to restore to its former condition the electrolyte flowing through the apparatus, and thus completing the cycle of chemical action, at the same time generating low voltage electric current. It is to be noted that in the apparatus shown in Fig. 1 this chemical ac- .tion can only take place when the mercury and sodium flow out of the electrolytic region.

In my second form of apparatus, shown in Fig. 2, I do not depend entirely upon the flow of the mercury in the cell to cause its removal out of the electrolytic region, but I also move the electrolytic region itself. In this form of the apparatus, instead of therebeing a single anode 15 and a single pole 16, as shown in the first form of the invention, there are, for each cell, a large number of electrodes or poles, each of which is used in succession as 'an anode of an electrolytic cell, the remainder being then used as poles of voltaic cells. These electrodes or poles are shown at 21, and the corresponding ones, or those in like order, in all the cells are connected by wires 22 to a common contact 23 in a terminal block 24. These contacts 23 are individually connected by wires 26 to spring contacts 27 which normally rest in contact with conductors 28 connected to a wire 29 which is connected bya wire 31 to the negative pole of an electric generator 33 and also by wires 32 to the several cathode bars 11. From the positive pole of said generator a wire 34 leads by a'wire 35 and individual wires 36 to contacts 37. Said spring contacts 27 carry rollers 38 which are arranged adjacent to the circumference of a cam roller or timer 39, having a raised portion 41. Said timer is rotated at any suitable speed, so that said raised portion 41 contacts with each roller in succession and then raises the roller so that the spring con- Each cell is thus com-' tact 27 moves out of contact with the conductor 28 and into contact with the contact 37. The slope of this raised portion is such that, just before each spring contact 27 moves out of contact with its corresponding contact 37, the next spring contact 27 of the series moves into contact with its contact 37, so that there is no interruption of the current flowing from the electric generator. It will be seen that, with this construction, each electrode 21 in succession is included in the circuit through the generator, so that the electric current generated thereby can pass through said electrode and through the pulp to the mercury cathode and then to the cathode bar and back to the generator, and the other electrodes are connected/directly with the'cathode bars 11 outside the apparatus and thus serve as poles of voltaic cells. In other words, the mode of operation of this form of apparatus is electrically similar to that of the first formfexcept that the position of that electrode which is in actual operation is constantly shifting. The parts are so arranged, that, first, the current from the generator passes through the lowermost electrode 21 the others being short-circuited through the cathode, then through the next higher electrode, and so on up to the uppermostelectrode. While the current from the generator is passing through any one electrode sodium cyanid is decomposed by electrolysis beneath said electrode, sodium is deposited upon the mercury cathode immediately beneath said electrode, and, upon the remaining surface of the mercury cathode, the reverse or regenerating process is taking place, that is, the sodium decomposes the water to form caustic soda, and nascent hydrogen is given off. The process applied to each portion of the. pulps is that, first, that electrolytic current is passed through the pulp, with the result before explained, and then this electrolytic. current is arrested for a period of time longer than the passage of the current and the chemical and voltaic action before described then takes place. All of the pulp is undergoing this process, although the difierent portions of the pulps are not similarly acted upon at the same time. One small portion, say onefifth, of the cell is electrolytic, and the remaining portion is voltaic. It will thus be seen that in this apparatus not only is the entire mass of'pulp moved over the whole of the cathode, but also the effect produced is the same as if the anode were moved over the whole of the cathode.

The difference between the two forms of apparatus is that in my first form, shown in Fig. 1, I remove the sodium generated by the electric current from the path of the traveling electrons, while in my second form, shown in Fig. 2, I. remove the path of the traveling electrons from the sodium.

The process is the same in both cases, namely, that of separating the sodium and the traveling or current electrons.

it is well known that, in the treatment of gold and silver bearing tellurid, arsenical, antimonial, as well as pyritic ores generally, ordinary cyanid solutions, that is, solutions to which other reagents have not been added, have up to the present time only yielded a partial gold and silver extraction, this result being due to the insolubility, and also to the reducing action, of the minerals incasing the gold or elements, as tellurium, combined with it. The addition of cyanogen bromid or iodid to the cyanid solution is found to greatly aid and improve the gold extraction; but the difficulty of preparing these reagents, together with their instability, and the excessive cost involved, has, in most cases, made their application useless or prohibitive. It has also been found that these halogen cyanids are entirely consumed at each application, and no means up to the present time have been known for the repeated and economical regeneration of these special reagents, so as to permit of the economical cyaniding of ores of the character referred to.

Now in the employment of my improved process for such rebellious ores, the ore, having been first crushed to a pulp, is discharged into the top of the apparatus with a certain percentage of sodium cyanid solution containing a haloid alkaline salt, such as sodium bromid. When passing between the anodes 15 and the cathodes 11, by the action of the electric current, electrolysis takes place of a certain portion both of the sodium cyanid and sodium bromid, which thereupon give up their sodium to the mercury and incidentally produce cyanogen bromid, which has the valuable efi'ect before referred to in improving the gold extraction, as the cyanogen bromid powerfully attacks a part of the gold, forming a gold cyanid or bromid, which readily dissolves in the remaining sodium cyanid solution present in the electrolyte. Now upon passing out of the' influence of the electrolytic current, the sodium decomposes water and caustic soda and nascent hydrogen are produced. The caustic soda and nascent hydrogen produce the very valuable result that they then reduce the free cyanogen bromid again to sodium cyanid and sodium bromid, while the gold is contained in an aurous cyanid solution. Any gold that is not procipitated from the cyanid solution by electrolysis in the apparatus can be recovered by ordinary methods such as the use of zinc dust, or preferably by the use of zinc anodes, as hereinafter more fully explained.

The value of the invention consists in that, whereas the powerful cyanogen bromid is very unstable, by this method any excess of unused cyanogen bromid is, until again needed, immediately converted into the stable compounds sodium cyanid and sodium bromid.

The following chemical reactions occur:

1. NaCnNaBr, employing a mercury cathode, gives, with the direct electrolytic current, sodium, and CnBr (cyanogen bromid) or other halogen cyanid according to the salt applied.

2. On being free from electrolysis, the sodium forms with water, sodium hydrate (NaHO), and nascent hydrogen.

3. These reagents reduce the cyanogen bromid according to the following equation:

lnBr2NaHO2HNaCnBaBr2H O.

The original reagents applied are thus regenerated. By this method there is substantially no loss of the cyanogen compounds, as, after having served their purpose in the electrolytic apparatus, they can be pumped back and used over again therein.

In the practical application of my improved process it is desirable for economy and other reasons to use two electrolytic machines or apparatus. In the first, A, of such machines there are used graphitized or other insoluble anodes 15*, and in the second machine, B, there are used soluble anodes 15", as zinc. In the first or upper machine, A, the main electro-chemical action takes place, while the lower machine B is used for the purpose of obtaining a further or more complete electro-deposition of precipitation of the gold contained in the electrolyte.

The lower. machine has soluble zinc anodes instead of insoluble graphitized carbon anodes'for the following reason. The sodium cyanid electrolyte is employed, as has already been explained, for two purposes. First, to render the larger particles of gold readily amalgamable by mercury, and, sec- 0nd, to dissolve the finer particles of gold, and form a soluble cyanid of gold and sodium. For the electrolytic recovery of gold from such solution of cyanid of gold and sodium, anodes might be used, as previously stated, which are insoluble, as graphitized carbon, but it is preferable to use soluble anodes as zinc, the chemical aflinity of which with cyanogen is very strong.

One advantage gained by using graphitized or other insoluble anodes in the primary electrolytic machine, instead of soluble or zinc anodes, is that the amalgam obtained in the mercury cathode cells where insoluble or graphitized carbon anodes are employed is a pure gold amalgam, free from zinc. Therefore the difficulty is avoided of separating the gold from the Zinc entering the mercury of the mercury cathode through the soluble zinc anodes. Also the insoluble or graphitized carbon anodes are necessary in the first or primary machine, because in this machine the nascent cyanogen is of distinct value for dissolving this fine, or nonamalgamable, gold. In the second or lower machine, in which the larger portion of the dissolved gold is deposited, the acid radicals formed at the anodes are no longer needed, and are highly detrimental to the thorough electro-deposition and saving of the gold.

In the second or lower machine, for the purpose of breaking up the double salts of the gold and sodium cyanid (AuNa(Cn) or AuNa(Cn),), I use at stated intervals a salt, as the sulfate of zinc, the addition being made in minute -'quantity in solution. This, by destroying the sodium cyanid in the electrolyte, allows of the instant electrode position of all gold still present in minute size in the solution.

The following statement will better explain the reaction involved. The solution of zinc sulfate added to the gold-sodium cyanid solution in the secondary, or soluble zinc-anode machine slowly forms zinc cyanid, aurous cyanid, plus sodium sulfate. The aurous cyanid and zinc cyanid, held in solution momentarily as colloids, are decomposed by electrolysis with the zinc anode, finally forming metallic gold, which is electrodeposited or precipitated in ,the mercury, and metallic zinc which also is electro-deposited. There probably also form the zincsodium cyanids which are washed away in the machine by the current of water continually flowing. The gold in the secondary or soluble (zinc) anode machine is present in solution as already noted, as gold-sodium cyanid. The solution of zinc sulfate, be ing slowly added to the cyanid electrolyte, breaks up this compound. The zinc, displacing the sodium, unites to form zinc gold cyanid, AuZn(Cn) while the S0 ions liberated from the zinc sulfate go over to the sodium to form sodium sulfate. This, while chemically inert in this instance, nevertheless greatly aids in the conductivity of the electrolyte. Gold-Zinc cyanid, being colloidal in minute amount in solution, nevertheless remains dissolved sutficiently long to instantaneously effect a complete electrodeposition or precipitation on to the mercury of the gold held in the electrolyte, this being accomplished by means of the soluble Zinc anodes employed, and during the continuous flow of the current.

In order to obtain complete extractlon and precipitation of the gold from the ore without using a very large number of such machines or apparatus, the pulp is taken from the tail of the first machine and is passed through an agitator 43 by means of a centrifugal pump 44* and is then delivered to the head of said machine to be again treated therein. This operation is repeated as many times as is necessary to obtain a thorough eonoes extraction of the precious values. After this extraction has been accomplished, the pulp is then passed on to the second machine, through which in like manner it is passed through an agitator 8 a number of times in succession by means of a centrifugal pump 44*, being agitated between each passage in the manner above referred to, until a thorough precipitation has been effected.

In the claims, for the purpose of brevity, wherever the word sodium is used, it is understood that potassium or other suitable alkaline metal or radical is to be regarded as an equivalent.

I claim 1. The method of recovering metal from metalliferous pulp which consists in passing the pulp with an electrolyte over mercury in a cell, passing a current of electricity through one portion of the cell to decompose the electrolyte, continually changing the path of said electric current through said cell, and continually removing the electricity generated in another portion of said cell by the chemical action of the components of the electrolyte.

2. The method of treating metalliferous pulp, which consists in mixing it with an aqueous solution of common salt, passing the mixture over a mercury cathode, electrolyzing the mixture to generate nascent chlorin and sodium, separating from one another the sodium and the current electrons to permit the sodium to form, with water, caustic soda and hydrogen, causing the nascent chlorin and the caustic soda to act upon the metalliferous particles, reuniting the uncombined caustic soda and chlorin to form common salt and assisting this reunion by conducting off the current of electricity generated thereby.

3. The method of treating metalliferous pulp which consists in mixing it with an aqueous solution of common salt, passing the mixture over a mercury cathode, electrolyzing the mixture to generate nascent chlorin and sodium, separating from one another sodium and the current electrons to permit the sodium to form, with water, caustic soda and hydrogen, causing the caustic soda to act upon the metalliferous particles, reuniting the uncombined caustic soda and chlorin to form common salt, and assisting this reunion by conducting off the current of electricitv generated thereby.

4. The method of treating metalliferous pulp which consists in mixing it with an aqueous solution of common salt, passing the mixture over a mercury cathode, electrolyzing the mixture to generate nascent chlorin and sodium, separating from one another sodium and the current electrons to permitv the sodium to form, with water, caustic soda and hydrogen, causing the nascent chlorin to act upon the metalliferous particles, re-

uniting the uncombiued chlorin and caustic soda to form common salt. and assisting this reunion by conducting ott the current of electricity generated thereby.

The method of recovering metal from metalliterous pulp, which consists in mixing the pulp with an aqueous electrolyte. passing an electric current to the electrode there through to decompose the electrolyte, separating the current electrons and the cathion component of the electrolyte and acting upon the pulp by an agent produced by the chemical action of the cathion on the water of the electrolyte.

(3. The method of recovering metal from metallit'erous pulp. which consists in mixing the pulp with an electrolyte, passing an electric current therethrough to decompose the electrol \'te'scpalating the current electrons and the cathion component of the electrolyte. and acting upon the pulp by an agent produced by the chemical action of said cathion with other components of the electrolyte. resulting from such sepa ation.

7. The method of treating metalliferous pnlp which consists in mixing it with an aqueous solution of common salt, passing the mixture over a mercury "athode, electrolyzing the mixture to generate nascent chlorin and sodium. separating from one another the sodium and the current electrons to permit the sodium to form, with water, caustic soda and hydrogen, causing the nascent chlorin and caustic soda to act upon the metalliterous particles, and reuniting the uncombined caustic soda and chlorin to form common salt.

8. The method of treating metalliferous pulp which consists in mixing it with an aqueous salt solution, electrolyzing the mixture to decompose the salt, removing the cathion component of the salt from the current electrons to permit it to decompose water, treating the metalliterous particles with an active agent so formed, and reuniting the uncombined constituents of the salt.

9. The method of recovering metal from metallit'erous pulp which consists in causing the pulp commingled with an aqueous electrolyte to flow in a stream over mercury, passing an electric current through the mixture to decompose the electrolyte, and then at a subsequent point in the path of the stream removing the current electrons to permit the electro-positive constituent to c0mbine with water, and acting on the metal with an agent resulting from said combination.

10. The method of recovering metal from metalliferous pulp which consists in cansing the pulp eommingled with an aqueous electrolyte to flow in a stream over mercury, passing an electric current through the mixture to decompose the electrolyte, and then at a subsequent point in the path of the stream removing the current electrons to permit the electro-positive constituent to combine with water, facilitating such combination by conducting away the electricity generated thereby, and acting on the metal with an agent resulting from said combination.

11. The method of recovering a precious metal from metallit'erous pulp which consists in first, passing over cells having mercury cathodes and insoluble anodes, the pulp mixed with a solution of compound of sodium and a radical which can attack the metal, passing a current of electricity between said anodes and cathodes, then passing the mixture over mercury in cells having cathodes and zinc anodes, and passing electric currents from said latter anodes to said cathodes.

12. The method of recovering metal from metalliterous pulp which consists in. first, passing many times in succession over cells containing mercuiy cathodes and insoluble anodes. the pulp mixed with an electrolyte, one of the constituents of which can attack the metal, agitating the same between each mssage, then passing many times in succession the mixture over mercury in cells having cathodes and soluble anodes, agitating the same between each passage and passing electriccurrents from said anodes to said cathodes.

13. The process which consists in mixing metalliferous pulp with a suitable electrolyte solution, causing said mixture to flow in a continuous stream, passing an electric current through the mixture to decompose said solution, then permitting the ions separated by the electrolysis to chemically react upon the pulp, and assisting said reaction by conducting away the electric current generated thereby, and then passing an electric current through the pulp so acted on to deposit the metal upon the cathode, while continuously supplying fresh mixture at the beginning of the stream to be so treated and continuously removing worthless material at the end thereof.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

WILLIAM A. HUSSEY.

\Vitnesses FRANCIS M. VVRIGIIT, D. B. RICHARDS. 

